1. Technical Field
Example embodiments of the present invention relate to wireless communication technology, and more specifically, to an antenna apparatus capable of minimizing interference between beams and maintaining a wide service coverage, and a method for handover using the same.
2. Related Art
A long term evolution (LTE)-Advanced and a worldwide interoperability for microwave access (WiMAX) currently under way for 4G mobile communication system development are a system that uses a frequency band below 6 GHz, uses a maximum 100 MHz bandwidth in the frequency band, introduces various wireless technology such as 8×8 multiple-input multiple-output (MIMO), carrier aggregation (CA), coordinated multi-point transmission (CoMP), and relay, and tries to secure a maximum transmission capacity of 1 Gbps.
Meanwhile, according to mobile data usage forecasting of wired/wireless service providers including mobile communication carriers and traffic forecasting research organizations, it is expected that the mobile data usage is up to 1000 times as today's data usage in 2020. This is a quiet reasonable prediction when taking into consideration that a mobile data usage rate is gradually changed from conventional voice or text services to video services requiring a higher transmission rate, and a use of smart terminal such as a smartphone and tablet rather than conventional general cellular phones is exponentially increasing.
As described above, as traffic usage exponentially increases and frequency efficiency improvement in a current cellular frequency band meets its limits, a new method of building a cellular network that uses a millimeter-wave (mmWave) frequency band from 10 GHz to 300 GHz in which a wider bandwidth expansion is available is considered.
When the millimeter-wave frequency band is used in mobile communication, it is possible to obtain a wide bandwidth of 1 GHz or more. Moreover, beamforming technology necessary for communication using the millimeter-wave frequency band is applied in addition to directionality that is a physical propagation characteristic of signals having the millimeter-wave frequency band. Therefore, since space resources and wireless resources such as a time, frequency, and code may be used, it is possible to dramatically increase a wireless capacity.
Currently, as examples in which the millimeter-wave frequency band is used in wireless communication, there is a wireless personal area network (WPAN) system having a short range of about 10 m focusing on a 60 GHz frequency band, or a case of point-to-point communication for wireless backhaul in a 70 to 80 GHz band. However, up to now, a use of the millimeter-wave frequency band is limited to a specific field.
When the cellular network (or cellular mobile communication system) using the millimeter-wave frequency band is implemented, it is possible to satisfy explosively growing mobile traffic demands using wide bandwidth frequency resources and space resource recycling. Therefore, it is expected that next-generation application services such as an ultra-definition (UD) image service may be easily provided with high service quality.
However, up to now, since a specific method of building the cellular network using the millimeter-wave frequency band has not been proposed, millimeter-wave frequency band has not been widely used.
For example, since a problem of interference between beams and a problem of service discontinuity due to handover failure during fast movement of terminal may exist when a plurality of beam are formed by using millimeter-wave frequency band, methods for overcoming the above described problems are required.